Three-story walk-up apartment buildings are common throughout the United States. Many of them were built 30 to 40 years ago. Given this vintage, the vast majority of these buildings are prime targets for energy retrofits, along with sorely needed improvements in comfort and indoor air quality (IAQ). In 2012, our company, Newport Partners, oversaw a deep energy retrofit on one of these buildings. The company, working with our partners, designed a retrofit scope to achieve ~50% energy savings while remaining cost-effective and working within the constraints of a tenant-in-place retrofit. We oversaw the implementation of the energy efficiency measures (EEMs) and measured actual performance once the work was completed. In other words, we found out what really happened, and how close our projections were.